BLOG - Geocoops

A hydrograph for a place with lots of trees will be dramatically different to one without as many trees. To begin with; the peak discharge will be much less due to the interception by trees, the trees intercept a lot of rain water and this is either stored in the tree or sits on the surfaces of the trunk, branches or leaves. The water on the surface is evaporated away and some of the water in the tree is transpired away, this process is called evapotranspiration. Next, water infiltrates through the ground with ease due to the roots of the trees breaking the ground. This infiltration makes surface flow rare because there are lots of gaps in the soil (due to the roots) and the trees take a lot of water up. So, the most common type of water movement is forest areas is through flow, this through flow is underground goes directly to the river. Through flows is very slow and this will influence the hydrograph because there will be a large lag time.
George Tilley 10o

Reply

Jack Hopwoods

20/1/2017 11:38:58 am

Explain how Afforestation will influence the shape of a hydrograph
Afforestation will make the hydrograph flat with a longer lag time:
The Hydrograph will have a smaller peak discharge because of the trees. When heavy rainfall occurs Interception will make the land on the leaves. This water will eventually be evaporated back into the atmosphere. Also, the majority of the water that has landed on the ground that is soaked into the soil through Infiltration will be absorbed into the trees through its roots. Once in the tree the water will eventually transpire out into the atmosphere. The evapotranspiration happening between these two reasons means less water is getting to the river meaning a lower peak discharge.
The hydrograph will have a longer lag time because when heavy rainfalls more water is infiltrated into the soil because the roots break up the surface. This means more water is travelling to the river as throughflow instead of surfaceflow as throughflow is much slower then surfaceflow it takes longer for the water to reach the river creating a longer lag time.
Explain how Urbanisation will influence the shape of a hydrograph
Urbanisation will make the hydrograph flashy with a shorter lag time:
The hydrograph will have a larger peak discharge because of the lack of trees. As there are virtually no trees in Urbanised areas less water will be sent to the atmosphere after heavy rainfall because there is no evapotranspiration, as there is no trees to soak water or intercept water. Because of this all of the water that has landed will go to the river creating a much larger peak discharge.
The hydrograph will have a shorter lagtime because of the concrete roads and pavements and also the drainage system. When there is heavy rainfall the rain will land on impermeable concrete and man-made infrastructure instead of soil. This means no water will be infiltrated into the soil, but will run to the river as surface flow instead which is much faster the throughflow. Also in most Urbanised areas a drainage system has been put in place. This rapidly reduces lagtime as the rain that has fallen into the area will go into drains and ejected into a river; this will very fast as it is designed to stop floods.

Reply

Dan Poynting 10M

20/1/2017 11:43:31 am

Explain how Afforestation will influence the shape of a hydrograph.
The hydrograph showing Afforestation would have a low peak discharge and the lag time would be much longer than normal. This is a flat hydrograph.
The reason the hydrograph would have such a low peak discharge is because of the trees. The water that would normally be entering the river doesn’t reach because of the trees. The precipitation falling is being intercepted by the trees. This is through a process called interception where the water from precipitation lands on the leaves of the trees. As well as this the trees are intercepting the water in the soil. This water is reaching the river via through flow, but the trees roots are intercepting that water on its way to the river. There is also lots of evapotranspiration which keeps the peak discharge low. Evapotranspiration is where evaporation ad transpiration happens at the same time. The water leaves the trees leave and out into the air.
The lag time is very long because the infiltration is very high, which is where water infiltrates the soil and runs to the river that way. This is because the roots from the trees have broken up the surface above. Therefore the water enters the river via through flow, which is much slower than the water flow to the river on the surface, which is called surface run off.
Explain how urbanisation will influence the shape of the hydrograph.
Urbanisation would mean that the hydrograph would have a high peak discharge and a short lag time. This is a flashy hydrograph.
The high peak discharge is because there is not anything intercepting the water on its way to the river. For example, there are not many trees which intercept the water, so all the water that falls, is taking to the river, rather than being intercepting by the trees.
The short lag time is because where houses and other buildings are built; the rock tends to be impermeable rocks. This is because it encourages overland flow. Impermeable rocks are rocks that don’t allow water into them. Because of this the water runs on the surface. The water can run into drains, which take it to the rivers. Therefore the water will reach the river quicker because drains or overland flow are much quicker than through flow.

Reply

Sam Pike

20/1/2017 11:43:40 am

Explain how Afforestation will influence the shape of the hydrograph
The hydrograph will have a low peak discharge because there will be high amounts of interception in the trees, so not as much precipitation will reach the ground. This is because the precipitation that has been intercepted will undergo evapotranspiration, which will also not reach the ground. The hydrograph will also have a long lag time, because the water will be transported to the rivers by groundwater flow, because the rocks are permeable, and so the soil doesn’t get saturated. So, because of the fact that the water has to be transported by groundwater flow (the slowest form of water transport) there is a high lag time as there is a long time between the rainfall and the peak discharge. The infiltration (vertical movement of water from surface storage to soil moisture storage) is high because the roots of the trees break up the surface, and they also absorb water from surface storage, meaning that water can easily pass through into soil moisture storage.
Explain how Urbanisation will influence the shape of a hydrograph
The hydrograph will have a high peak discharge because there will be low amounts of interception, because there are not many trees, meaning that all of the water will reach the ground, as no interception and therefore evapotranspiration will not take place as there isn’t much vegetation, and lots of impermeable buildings. All of the rainfall goes into the drains, which very fast, and therefore the peak discharge is very high, and also the lag time is very short as the drains are very short. Infiltration is low as there isn’t many trees to break up the soil and the rock is impermeable.

Reply

Bob Thain

20/1/2017 11:44:36 am

Explain how afforestation will influence the shape of a hydrograph
The hydrograph in an area where afforestation takes place would have a lower peak discharge and a longer lag time than a hydrograph taken in an area without afforestation.
The hydrograph of this area would have a lower peak discharge than usual due to the trees in that area. The trees influence the hydrograph because the water that would usually enter the river is taken up by the trees through their roots. The peak discharge can also be affected by the trees intercepting the rain that’s falling that would otherwise go into the river.
The lag time is longer than usual as well as the trees not only stop some of the water going to the river but they also slow it down as well. Interception is a factor of this as the water is held on the leaves and it doesn’t allow all the water to get to the river at the same time, which helps reduce flooding as there won’t be as much water passing through at the same time.

Explain how urbanisation will influence the shape of a hydrograph
The hydrograph in an urban area would have a short lag time and a high peak discharge than a hydrograph in a non-urbanised location.
The hydrograph in this area would have a higher peak discharge than usual due to there being very little evapotranspiration as there is a general lack of greenery in these urban areas. This along with the fact that water enters the rivers extremely quickly and all at the same time roughly, leads to a high peak discharge.
The lag time is shorter than usual as well as the drainage systems in urban areas are generally very quick due to the high populations of these areas, so the water flows to the river quicker than if it was on the surface of underground.
Bob Thain 10J

Reply

Jamie barker

20/1/2017 11:52:39 am

Explain how afforestation will influence the shape of a hydrograph?
The hydrograph will have a low peak discharge and be a flat graph. This happens because the trees intercept water. When it rains the trees remove the water that is in the soil. The trees then take the water up and it is stored. This is where the water then evaporates and transpires back into the atmosphere. The hydrograph will also have a long lag time. This is because a lot of the water infiltrates in to the ground as through flow. This means the soil will never become saturated and no surface flow will form.
Explain how urbanisation will influence the shape of a hydrograph?
The hydrograph will have a high peak discharge and be flash graph. This happens because the cities line the ground with tarmac and concrete which means the rain cannot infiltrate as the tarmac as it is impermeable. The hydrograph will also have quick lag time. This is because the drains take water to the river which means it is filled quickly and floods.

Reply

Thomas Brewis-Watters

20/1/2017 11:52:52 am

Explain How Afforestation Will Influence the Shape of a Hydrograph
The hydrograph will have a low peak discharge, as lower amounts of water will enter the river. This is because there will be more trees able to remove more water from the soil. Also, there will be higher amounts of interception, if there are more trees. This means that lower amounts of water will be able to reach the ground, meaning more of the rainfall will undergo the process of evapotranspiration.
In addition, there is long lag time. This is because infiltration is high, as the tree’s roots break up the ground’s surface. This means the majority of the rainfall (not intercepted by the tree’s leaves) will enter the soil.
This means that the hydrograph will be a flat hydrograph, with a low peak discharge and a long lag time.
Explain How Urbanisation will Influence the Shape of a Hydrograph
The hydrograph will have a high peak discharge. This is because urban areas have fewer trees, meaning lower rates of interception and evapotranspiration, leading to more water being able to reach the ground. .
In addition there is a short lag time due to drainage systems. This is because higher amounts of water will be transported quickly from the ground to the rivers.
This will mean that the hydrograph will be a flashy hydrograph, with a high peak discharge and a short lag time.

Reply

Ewan Laird

20/1/2017 11:54:22 am

Explain how Afforestation will influence the shape of the hydrograph

The hydrograph of an area with lots of vegetation and forest will have a low peak discharge. This is because the trees will intercept a lot of the water. The soil around the trees will be unsaturated because trees soak up the water and store it. The water sucked up by the trees will evaporate and transpire back into the atmosphere. The hydrograph has a long lag time because there is no surface flow and lots of through flow. This is because the soil is unsaturated and can soak up the precipitation, there is lots of through flow which means a long lag time.

Explain how urbanisation will influence the shape of the hydrograph
The hydrograph will have a high peak discharge and be a flashy graph. This is because there is less exposed ground because of the roads, pathways and buildings; this means more surface flow and a higher peak discharge. The drainage system in an urban environment means all of the city’s water usage will be directed into the river meaning the discharge is higher. An urban environment means a shorter lag time. There is very little vegetation in a city, this means there is no trees or plants to soak up the water in the saturated soil, because infiltration cannot occur there is lots of surface flow meaning a faster lag time.

Hydrographs 20th January 2017
Explain How Afforestation Will Influence the Shape of a Hydrograph
In areas afforestation the hydrograph will have a low peak discharge. This is because there is less water and therefore less water reaches the river, creating a lower peak discharge. This is caused beaks the tree roots break up the ground making the soil unsaturated and allows it to store more water underground which does not reach the river. This also means that the ground will never become saturated and have surface flow that would increase the peak discharge. The river will also have a longer lag time. This is because the water takes longer to reach the river due to interception by the vegetation such as trees. The trees break up the ground (as mentioned (earlier). They then suck up the water from their roots, making the water take longer to reach the river by groundwater or through flow.

Explain How Urbanisation Will Influence the Shape of a Hydrograph
In areas of urbanisation the hydrograph will have a high peak discharge. This is because there is more water and therefore more water reaches the rivers. The waters path to the river is also easier as the ground is often concrete and therefore saturated meaning the water does not get absorbed by the soil and is all surface flow so reaches the river. The hydrograph will also have a small lag time due to the saturated ground meaning the water will run smoothly and quickly.

Marcus Churchill 10J

Reply

Jay

20/1/2017 11:57:26 am

Explain how afforestation will influence the shape of a hydrograph
The hydrograph in an area where afforestation takes place will have a smaller peak discharge and a longer lag time. The hydrograph will have a low peak discharge because less water is getting into the river. This is caused by trees absorbing the water in the ground. This makes the soil unsaturated meaning less water will infiltrate into the ground water storage therefore less water will flow into the river through groundwater flow. Also, the hydrograph will have a longer lag time because it takes longer for the water to reach the river. This is caused by trees and vegetation intercepting rainfall meaning less water will make it into the ground. Therefore less water will enter the river through groundwater flow meaning it will take longer for peak discharge to be reached.

Explain how urbanisation will influence the shape of a hydrograph
The hydrograph in an area where urbanisation takes place would have a higher peak discharge and a shorter lag time. The hydrograph will have a high peak discharge because very little interception will take place as there won’t be that much vegetation in the area. Also, there will be a shorter lag time as all the buildings in the area are impermeable. Therefore all the water will run of in the drains and will enter the river very quickly.

Reply

Daniel Parsons

22/1/2017 12:47:49 pm

How does Afforestation Influence the Shape of a Hydrograph?
The Hydrograph would have a low peak discharge. This is because there would be a lot of interception going one because of all the trees. The trees stop rain from getting to the ground and it evaporated off the leaves. Also water that has infiltrated into the soil will also be absorbed by the roots of the trees and then transpired off the leaves. This means that not very much water would actually get to the river let alone actually infiltrate the soil. This means that the water in the river is lower than usual.
The graph would also have a long lag time. This is because there is a high rate of infiltration which means that the water has to travel above the water table via through flow. This is slow and also the fastest movement which is surface flow but that doesn’t really happen because there the infiltration is too high for the water to stay on the surface.

How does Urbanisation Influence the Shape of a Hydrograph?
The hydrograph would have a high peak discharge because the water heads directly to the river in a high volume when there is a storm or lots of precipitation.
The Hydrograph would also have a short lag time because the building would be made from impermeable rock so there would be surface run off which would go to drains. Drains are a very quick and effective way of getting water to the river and there would be nothing to get in the way of the water.

Reply

Charlie Britton

22/1/2017 03:34:41 pm

Explain How Afforestation will Influence the Shape of a Hydrograph
The Hydrograph will be very flat and the rising and falling limbs will be quite long and not very high. Therefore, we will see a low peak discharge. This is because there is a lot of water stored in the trees (also known as interception). The water is easily stored in the trees when it rains and it flows out of the trees much slower or evaporates in the process. Therefore, we will experience less overall flow through to the ground and there will be a much more consistent rate of flow. The Hydrograph also shows a long lag time and this is because it takes a long time for the water to flow through the trees and into the groundwater flow. Because there is a lot of trees to break up the surface, more water will be able to easily infiltrate and be moved horizontally by through flow. This also means that there will be less surface flow and surface flow is quicker than through flow so would create a flashier Hydrograph.

Explain how urbanisation will influence the shape of a Hydrograph.
The Hydrograph will have a high peak discharge in an urbanised area with fast rising and falling limbs. This is because there is lots of concrete in the roads and houses will mean that lots of the rain will have to use surface flow to get to a drain where it will flow somewhere else. The inside of a drain is hollow so even though the water is going underground, it still travels at a rate similar to surface flow. Many of these drains lead off to the rivers creating a shorter lag time and a higher peak discharge as it only takes a few minutes for the rainwater to get to the river compared to the few hours it takes for rainwater to get to the rivers via through flow. As there are not many places for the rain to infiltrate into the ground, most of the water flows via surface flow.